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Old 09-27-2016, 04:18 PM   #61 (permalink)
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HELP ME FIGURE THIS ONE OUT!

OK, so since yesterday the short trips around my street and all the other system testings checked ok... I decided to take the car out around town and drive it in the highway and see how the car reacted.

So I got some temporary DMV tags and when out and about riding. I put in about 20 or so city miles, and about 10 or so highway yesterday. Plus some more aggressive engine loading / city driving today to promote ring seating. (I even got the car inspected today)

So far everything works great... EVEN THE SPEEDOMETER / ODOMETER ARE REGISTERING CORRECTLY...
And that's my problem... I was expecting my speedometer & odometer readings to be off, so from the start I downloaded a speedometer w/ odometer app on my phone so that I could track my "GPS" speed vs my "GAUGE" speed... But my dash speedometer & odometer where accurate to within 1 mph all the way though the speed spectrum up to 75phm... accurate the whole way through!!!

So of course, now my mind was racing to try to figure out why...
If I just installed a 3.52 tranny, on a formally auto car, how can my speedometer be accurate? Could it be that I was tricked and was sold a non-3.52 tranny? But it definitely came out of a four cylinder because the linkage support was in the 1.3L location...

So from the info on this web thread I came away with two things:
1- the driven (17/18 tooth) gear is basically interchangeable between different but similar diameter tire sizes... which means I could have gotten extremely lucky and have the perfect gear/tire combo for my speedometer
2- all pre'95 1.3 MT would have a 3.52 ratio, but all post'95 MT would have a 3.95 ratio which is the same as the automatic transmission ratio originally in my car !!!

So this thread somewhat collaborates that there is a 1.3MT w/ the same final ratio (3.944/3.95) as the automatic that my car was once equipped with, except they don't classify it as pre or post '95, instead its classified as FWD?

Could I have been duped, and sold a fake!!!

So I took a look at the transmission identification markings:
M244860 M= indicates 1991

So now I was confused, pre'95... but what did FWD stand for?
Could I have a 3.944 ratio transmission? I have been unable to decode the rest of the numbers to find gear ratio.

So the next best thing is to drive at a fixed speed and obtain RPM, and tire size and do the math to figure out final drive ratio...

So I installed a little cheap universal induction RPM gauge that I had recently purchased for something else...



This is what I came away with"
1,300 rpm @ 40 mph
1,750 rpm @ 55 mph
2,100 rpm @ 60 mph




Using these figures and my tire size revs/per mile I tried multiple combinations of gear ratios and none fit the bill... It comes out that I have a final drive ration of 2:1 - 2.26:1... which I know is not right... So now I have to question the accuracy of the RPM gauge.

HELP ME OUT... What do you guys think.

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Old 09-27-2016, 04:19 PM   #62 (permalink)
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I think I like the backpack frame idea... It's supper light weight, and may come in handy... I'll keep that idea floating around for when I go yard sale hopping with the wife. Thanks
Happy to help. It's most comfortable installed upside-down. And mine is missing the shoulder straps so it's not dual use.

Maybe when I get the hinge on the Koolatron refrigerator fixed and it's reinstalled, I'll get a picture of the interior.

Quote:
HELP ME FIGURE THIS ONE OUT!
Jack it up, turn the engine over by hand and count the wheel revolutions?
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Old 09-27-2016, 04:54 PM   #63 (permalink)
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Simple one - is the tacho set for three cylinders? Does it read accurately when compared to a known one?

2100 rpm at 60mph on those teensy wheels sounds wrong to me.

Simon
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Old 09-27-2016, 04:59 PM   #64 (permalink)
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With my 99 I'm at 2200 rpm at 45 mph. Sounds like you got the right trans to me.
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Old 09-27-2016, 06:00 PM   #65 (permalink)
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Here's an equation for MPH when you know GEAR, AXLE and engine RPM:

MPH = (60/(G*A))*(RPM/rpm)

where:
MPH = vehicle speed, miles-per-hour.
RPM = engine speed, revolutions-per-minute.
rpm = tire speed, revolutions-per-mile.
60 = conversion constant, minutes-per-hour.
G = transmission GEAR ratio.
A = final drive AXLE ratio.

Tire revolutions-per-mile (rpm) data obtained from tire manufacturer, but may also be estimated as 97% of tire diameter:

rpm ≈ 20792/tire diameter(inches)

where: 20792 = 20168/0.97; and 20168 = 5280*12/3.14159...

Last edited by gone-ot; 09-27-2016 at 07:06 PM..
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Old 09-27-2016, 09:03 PM   #66 (permalink)
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Quote:
Originally Posted by MPGeo View Post
[SIZE="3"]So from the info on this web thread I came away with two things:
1- the driven (17/18 tooth) gear is basically interchangeable between different but similar diameter tire sizes... which means I could have gotten extremely lucky and have the perfect gear/tire combo for my speedometer
2- all pre'95 1.3 MT would have a 3.52 ratio, but all post'95 MT would have a 3.95 ratio which is the same as the automatic transmission ratio originally in my car !!!

So this thread somewhat collaborates that there is a 1.3MT w/ the same final ratio (3.944/3.95) as the automatic that my car was once equipped with, except they don't classify it as pre or post '95, instead its classified as FWD?

Could I have been duped, and sold a fake!!!

So I took a look at the transmission identification markings:
M244860 M= indicates 1991

So now I was confused, pre'95... but what did FWD stand for?
Could I have a 3.944 ratio transmission? I have been unable to decode the rest of the numbers to find gear ratio.
That site is wrong. These are the manual trans final drives used in 2WD Swifts and Metros. There's nothing to decode on the trans besides the year, you have to count gear teeth to determine which ratio you have.
3.52 - 1989-1994 SOHC 4-cyl Swift
3.79 - 1989-1994 Metro XFi and 1995+ SOHC 4-cyl Swift/Metro
4.10 - 1989-1994 3-cyl Metro and 1989-1994 DOHC Swift GT/GTi
4.39 - 1995+ 3-cyl Metro and Metro convertible
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Old 09-27-2016, 09:48 PM   #67 (permalink)
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Quote:
Originally Posted by freebeard View Post
Happy to help. It's most comfortable installed upside-down. And mine is missing the shoulder straps so it's not dual use.

Maybe when I get the hinge on the Koolatron refrigerator fixed and it's reinstalled, I'll get a picture of the interior.

Jack it up, turn the engine over by hand and count the wheel revolutions?
You know, I was thinking about a fridge myself... Would love to see it.
And the jacking it up and counting tire revs is not a bad idea. I can mark the tire with a chalk line and should be able to see the difference between 3.5 or 3.9 revs pretty easy... I think I will try this. Thanks.


Quote:
Originally Posted by Daox View Post
With my 99 I'm at 2200 rpm at 45 mph. Sounds like you got the right trans to me.
Thank you for the real-world #s that I can compare to...
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Old 09-27-2016, 10:08 PM   #68 (permalink)
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Quote:
Originally Posted by Old Tele man View Post
Here's an equation for MPH when you know GEAR, AXLE and engine RPM:

MPH = (60/(G*A))*(RPM/rpm)
Thanks for the formula... I had done plenty of math on this by making up my own formulas... which turned out were fairly accurate.

With this formula, still none of the mentioned ratios worked... I reversed the formula to solve for A, and still... I'm looking at a 2.3'ish:1 ratio depending on which 5th gear ratio I decided to use...

So something is still off... The only two variables left to play with in the formula are the accuracy of the tire rev/mile (927) and the accuracy of the tach readings... And probably my RPMs are to blame.

But thanks for the Formula. Much appreciated.



Quote:
Originally Posted by LittleBlackDuck View Post
Simple one - is the tacho set for three cylinders? Does it read accurately when compared to a known one?

2100 rpm at 60mph on those teensy wheels sounds wrong to me.

Simon
Yeah, at first glance it seemed wrong to me too...

The tachometer is and induction type, so there are no cylinder setting... No different than a timing light.

Now you do bring a valid point in relation to its accuracy, which I had questioned as well...

I don't have any other tachometers laying around, and definitely not a 3cyl one... But I do have other vehicles with OEM tachs, the Mazda and the Disco both have wires... I can test the e-bay tach's accuracy against those two OEM tachs and see what I get. Thanks

Last edited by MPGeo; 09-27-2016 at 10:16 PM..
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Old 09-27-2016, 10:30 PM   #69 (permalink)
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If you have a 'smart' phone, I hear they have tachometer apps.

Last edited by freebeard; 09-28-2016 at 12:30 AM.. Reason: here≠hear
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Old 09-27-2016, 11:22 PM   #70 (permalink)
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Gasoline fumes lists the only ratios I have seen. I ran Metros for 8 years. Since the transmission drive gear is attached to the crown gear you change the driven gear to correct for tire size only. The 3.5 tranny came in sohc 1.3 Swift from 89-94, the 3.8 tranny came in 95+ 1.3 Metros and 89-94 Xfi . The 4.1 ratio came in base Metros from 89-94 and Swift Gt dohc 1.3 cars, the 4.4 ratio transmissions came in the 95+ 3 cylinder Metros.

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